Such a valve arrangement is known from WO 2004/055387 A1.
Machines and devices performing hydraulic functions are usually connected with several consumers, each being controlled via a control valve. For example, a backhoe has several hydraulic cylinders, each lifting a different section of a boom, a rotary motor, with which the uppercarriage can be turned in relation to the undercarriage, and if required a further hydraulic function for activating a grab or a chisel located at the end of the boom. Similar conditions exist in other devices with hydraulic functions, for example, working platforms, tractors or agricultural machines, etc.
In this connection, each individual control valve is located in a valve module. The valve modules are combined to a block or a battery-like unit. This block is supplied with pressurised hydraulic fluid via a high-pressure connection. Depending on the position of the valve elements of each individual control valve, the hydraulic fluid from the high-pressure connection is then passed on to an outlet with a more or less large volume flow or with a more or less high pressure. For example, the control valves can be proportional valves, which permit a predetermined volume flow of hydraulic fluid to the working connection and thus to a consumer, depending on the position of a valve element.
Working devices and machines, which perform hydraulic functions, involve potential risks. Accordingly, a relatively high safety standard is required. Above all, it is desired to avoid that people get hurt, when faults occur.
Faults could, for example, occur in that the valve element is not displaced in the manner specified by the control signals. This can, of course, be controlled directly by means of the position sensor. However, under certain circumstances, this control can also be faulty.